Add the Snapshot interface

snapshot/thread_snapshot.h

Index: snapshot/thread_snapshot.h
diff --git a/snapshot/thread_snapshot.h b/snapshot/thread_snapshot.h
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+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_SNAPSHOT_THREAD_SNAPSHOT_H_
+#define CRASHPAD_SNAPSHOT_THREAD_SNAPSHOT_H_
+
+#include <stdint.h>
+
+namespace crashpad {
+
+struct CPUContext;
+class MemorySnapshot;
+
+//! \brief An abstract interface to a snapshot representing a thread
+//!     (lightweight process) present in a snapshot process.
+class ThreadSnapshot {
+ public:
+  //! \brief Returns a CPUContext object corresponding to the thread’s CPU
+  //!     context.
+  //!
+  //! The caller does not take ownership of this object, it is scoped to the
+  //! lifetime of the ThreadSnapshot object that it was obtained from.
+  virtual const CPUContext* Context() const = 0;
+
+  //! \brief Returns a MemorySnapshot object corresponding to the memory region
+  //!     that contains the thread’s stack.
+  //!
+  //! The caller does not take ownership of this object, it is scoped to the
+  //! lifetime of the ThreadSnapshot object that it was obtained from.
+  virtual const MemorySnapshot* Stack() const = 0;
+
+  //! \brief Returns the thread’s identifier.
+  //!
+  //! Thread identifiers are at least unique within a process, and may be unique
+  //! system-wide.
+  virtual uint64_t ThreadID() const = 0;
+
+  //! \brief Returns the thread’s suspend count.
+  //!
+  //! A suspend count of `0` denotes a schedulable (not suspended) thread.
+  virtual int SuspendCount() const = 0;
+
+  //! \brief Returns the thread’s priority.
+  //!
+  //! Threads with higher priorities will have higher priority values.
+  virtual int Priority() const = 0;
+
+  //! \brief Returns the base address of a region used to store thread-specific
+  //!     data.
+  virtual uint64_t ThreadSpecificDataAddress() const = 0;
+
+ protected:
+  ~ThreadSnapshot() {}
+};
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_SNAPSHOT_THREAD_SNAPSHOT_H_